1. Technical Field of the Invention
This disclosure relates to a two-way wireless communication device, and more particularly, to a wireless communication device such as a transceiver that is capable of automatically switching between transmission and reception modes in a handset.
2. Description of the Related Art
In cases where a user wishes to transmit his voice using a conventional wireless communication device such as a transceiver, the user manually activates a push-to-talk switch (hereafter, a ‘PTTSW’) to transition from stand-by (reception) mode to transmission mode. The user may then transmit his voice to his counterpart.
After the user informs his counterpart that he is finished transmitting (often indicated by voicing phrases such as “please”, “please respond”, or “over”), he releases the PTTSW to switch from transmission mode to reception mode in order to hear the voice of his communication partner. Since communications are made to each other using a single radio frequency carrier wave, this communication system is commonly known as a “half-duplex” type of system.
Other conventional wireless communication methods are such that a user's transmission and reception frequencies are different, and each is used as his counterpart's reception and transmission frequency, respectively. Thus the party can speak and hear freely, just like using a regular telephone. This system is commonly categorized as “full duplex.”
In the simplest case of a conventional full-duplex wireless communication device, both the base unit and the handset transmit and receive radio waves with all of the power sources (including those for the transmission part and the reception part) are kept turned on both during stand-by and actual communication. Because the transmission part usually consumes far more power than the other parts, the power supply for the transmission part imposes a heavy burden on the handset, especially when a small and portable handset is required.
FIG. 1 is a block diagram that illustrates an improved, conventional, “full-duplex” wireless communication device that turns the power source of the transmission part on only when transmission is being performed with the handset and/or the base unit.
Referring to FIG. 1, the device includes a wireless part, a control part, and a transmitter/receiver part, each of which are indicated by dashed lines. A reception antenna 1 in the wireless part picks up a reception signal, which is sent to the reception part 150. The reception part 150 includes a high frequency amplifier 2, a reception mixer 3, an intermediate frequency (IF) amplifier 4, and a FM demodulator 5. After being processed in the reception part 150, the reception signal is transmitted to a receiver 8 in the transmitter/receiver part via switch 6 in the control part. Normally, switch 6 is always turned on.
A transmission signal from a transmitter 11 in the transmitter/receiver part is emitted in the form of radio waves from a transmission antenna 19 in the wireless part. A switch 12 in the control part couples the transmission signal to a transmission part 151 in the wireless part. The transmission part 151 includes a FM demodulator 16, a transmission mixer 17, and a transmission power amplifier 18.
The control part is further equipped with a PTTSW 9 by which manual input is given to a transmission/reception switch controller 10. The switch controller 10 controls the switches 6 and 12 and a transmission part power source 20.
When the PTTSW 9 is not manually activated, the wireless communication device emits no radio waves and is set in reception mode where the switch 12 and the transmission part power source 20 are turned off.
To initiate communications, the PTTSW 9 is pushed down, activating both the switch 12 and the transmission part power source 20. A person at the other end is called, who must then depress his own PTTSW to answer the call. During communication, both PTTSWs should be turned on. When communication is over, each user turns off their PTTSW.
According to this wireless communication device, total power consumption is reduced because the power in the transmission part is consumed only when the PTTSW 9 is pushed down (“On” condition).
The details regarding the control part in FIG. 1 during each mode of operation are described below. The base unit and the handset have the same structure, and are operated in the same manner, exchanging different transmission and reception frequencies.
In stand-by mode (no radio wave is emitted): PTTSW 9 is off (open circuit); switch 6 is on, connecting receiver 8 to FM demodulator 5; switch 12 is off, placing transmitter 11 in an open circuit; and transmission part power source 20 is turned off.
In communication mode (radio wave is emitted): PTTSW 9 is on; switch 6 is on; switch 12 is on, connecting transmitter 11 to FM modulator 16; and transmission part power source 20 is turned on.
FIG. 9 is a block diagram illustrating a conventional “half-duplex” wireless communication device. When compared with the “full-duplex” device of FIG. 1, the half-duplex device differs from FIG. 1 in that the transmission and reception signals are each transmitted/received from a common transmission-reception antenna 22 via a switch 21. Further, the transmission/reception switch controller 10 controls the switch 6 and the switch 21 as well as the switch 12 and the transmission part power source 20.
The wireless communication device emits no radio wave when the PTTSW 9 is not manually pushed down. In this reception mode the switch 21 is connected to the reception part 150 and the switch 6 is turned on, while the switch 12 and the transmission part power source 20 are turned off.
To start communication, the PTTSW 9 is pushed down for transmission mode. The switch 21 connects to transmission part 151 and the switch 6 is turned off, while the switch 12 and the transmission part power source 20 are turned on. Communication is then started with words such as “hello”, so that the person at the other end is called. Response from the counterpart is promoted with words such as “please” at the time of completion of transmission, then the PTTSW 9 is turned off returning the device back to reception mode.
When the counterpart receives words such as “please”, which is a sign of completion of transmission, he/she pushes down his/her PTTSW 9 changing the counterpart device to transmission mode. The counterpart device then starts a reply transmission. At the end of his/her reply, a sign of completion of communication such as “please” is transmitted. The PTTSW 9 in the counterpart device is turned off returning the device back to the reception mode. In this manner, communication is conducted between the two wireless communication devices.
The control part in FIG. 9 operates as follows. The base unit and the handset have the same structure, and act in the same manner with the same transmission and reception frequency. In the stand-by mode PTTSW 9 is off, switch 6 is connected to receiver 8, switch 12 is disconnected to transmitter 11, switch 21 is connected to reception part 150 (to High frequency amplifier 2). In the transmission part 151 the transmission part power source 20 is off and no radio wave is emitted.
In the transmission mode, the PTTSW 9 is turned on disconnecting switch 6 from receiver 8, connecting switch 12 to transmitter 11, and switching switch 21 to transmission part 151 (transmission power amplifier 18). In transmission part 151, the transmission part power source 20 is turned on and a radio wave is emitted.
In the reception mode the PTTSW 9 is turned off connecting switch 6 to receiver 8, disconnecting switch 12 from transmitter 11, and switching switch 21 to reception part 150 (High frequency amplifier 2). In the transmission part 151, the transmission part power source 20 is turned off and no radio wave is emitted.
As is described above, the difference between the full-duplex and the half-duplex systems is summarized as follows. In the full-duplex system, similar to a telephone system, both users may simultaneously transmit and receive signals. In the half-duplex system, one user cannot break into the other's speech so long as the other is talking. Therefore, the PTTSW is indispensable in the half-duplex system for switching communications between the two users.
The conventional wireless communication device such as a transceiver is widely used as a handy, communication-switchable, wireless device. However, communications cannot be made without manually pushing the PTT switch. This makes it impossible to communicate when the user's hands are not free to push the PTT switch. Examples of such situations include communications between a racing car driver and his/her pit crew and communications between a firefighter and his/her fire crew.
As is described above, if the full-duplex system without the PPT switch 9 is used, both hands may be freely used (hands-free), but the power source 20 of the transmission part remains turned on increasing consumption of the power source (battery). Therefore, the system cannot be continuously operated for a long time period.
A headphone may be used for containing the transmitter/receiver part of the handset in order leave the user's hands free. However, the microphone in the headphone type handset often picks up noise and voice around the user, deteriorating voice quality.
To reduce this problem, the microphone can be located in an earphone that is inserted into a user's external ear canal, while the other ear canal is occupied by a speaker earphone. However, in this case, both ears are occupied with the microphone and the speaker. This prevents the headset operator from hearing other peripheral sounds and voices, which often causes crucial inconvenience.